According to the state of technology, the pressure in a transmission, especially in an automatic transmission for motor vehicles, is regulated in a hydraulic circuit based on demand. While the pressure level in the hydraulic circuit can be kept low for the lubricating oil supply of the transmission parts. The pressure must be greatly increased during the shifting process in order, for example, to be able to quickly fill the shift elements.
Normally for the regulation of pressure in hydraulic circuits, pressure regulators are used, which control slides for clutch activation. The control of the slides occurs within the pressure regulator by way of a proportional magnet, which consists of a magnetic core, a magnetic coil and an armature. In the process, the coil current is power-controlled via the proportional magnet in proportion to the output value; the armature and thus the slide for clutch control are controlled according to the coil current. The characteristic curve desired for clutch adaptation is produced from the resulting characteristic magnetic force-current curves of the pressure regulator in the electro-hydraulic control system of the automatic transmissions.
DE 199 43 066 describes an electromagnetically activated, hydraulic proportional valve with a magnet part consisting of an electrically controlled coil, a fixed core extending into the interior of the coil and a movable armature acted on by the coil, which armature is coupled with a closing member and with a valve part comprising at least an intake channel, a return channel and an operating channel, as well as a valve seat through which an effective connection with the closing member controls a fluid connection between the operating channel and the return channel. At least in the area of its end facing the valve seat, the closing member comprises a basic cone-shaped, sealing body whose smaller front face is turned toward the valve seat, whereby the sealing body comprises at least one stall edge on its end facing away from the valve seat.
This configuration should permit the hydraulic proportional valve to behave in a stable manner with respect to temperature influences and oscillation excitation caused by the flow. The pressure/current characteristic curves of the proportional valve have a more constant and more stable course compared to customary pressure control valves, since the sealing properties and the wear behavior of this proportional valve are improved.
Another proportional, pressure control valve is described in DE 199 04 901 of the Applicant, whereby this proportional, pressure control valve is constructed as a relay valve with a pressure reduction and a pressure maintenance function. The valve consists of a valve housing with inflow and outflow openings, a control element, an armature rod and a proportional magnet, which consists of a magnetic core, and armature and a magnetic coil. The proportional magnet manifests an almost constant magnetic force in its operating range. In the stop position of the armature, the smallest axial separation between the armature and the magnetic core is dimensioned such that the magnetic force between these two parts in the stop position is greater than the magnetic force in the operating range of the proportional magnet, where the armature can be fixed in the stop position by means of this magnetic force.
Finally, a proportional, pressure control valve is known from DE 100 34 959 of the Applicant, including a valve part, inflow and outflow openings and at least one closing part to control an aperture and one of the openings, as well as a magnet part with a magnetic core, a magnetic coil and a displaceable armature. Working together with the armature is the activation element, which activates the closing part, especially at the aperture of the inflow opening, where the activation element penetrates at least partially into the aperture during the control process. The effective hydraulic cross-section of the aperture is thereby basically determined by the aperture length, the aperture diameter and the diameter of the activation element in the aperture.
With regard to an optimized flow rate in the valve part, especially in the range of lower temperatures, i.e., at higher viscosities of the hydraulic fluid and with regard to lower flow resistances, this proportional pressure control valve comprises an optimized supply geometry determining the flow rate, i.e., the relation of the aperture length to the aperture diameter is selected less than 2.0, where this aperture determining the flow rate is positioned, in particular, in the inflow opening of the valve. This way, this valve has lower flow losses, especially at high oil viscosities, i.e., at lower temperatures; higher throughput quantities and shorter response times are hence achieved for the valve, whereby this proportional pressure control valve facilitates better dynamic values.
In automatic transmissions on motor vehicles, a hydro-dynamic converter is used as the starting element. The energy requirement for this component part is especially high with cold transmission oil, which affects the starting behavior of the vehicle. In addition, the response behavior of the transmission shift clutches is correspondingly delayed in the minus temperature range, which is also perceived to be unpleasant.
It is the goal of this invention to create a proportional, pressure control valve, with which an increase of the dynamic control capability of power shift clutches, especially the starting clutch in automatic transmissions, is achieved without a hydrodynamic starting element and the gearshifting clutches for motor vehicles.